1. Field of the Invention
The present invention relates to an ultrasound flexural transducer.
2. Description of the Related Art
European Pat. No. EP-B-0 075 302 discloses a sensor for making a distance measurement based on the ultrasound echo principle. This sensor is intended to serve for the calculation and display of distances between a vehicle and obstructions in the near region. This device uses an insulator-type transducer which has a piezo-ceramic oscillator mounted therein. Damping material which prevents a high-energy ultrasound emission or signal emission is provided on the inside of the membrane of this insulator-type transducer at two horizontal circular segment positions which are opposite to each other. The damping material may, for example, be soft rubber. The insulator-type transducer is formed as a horn radiator in the above-recited reference.
The membrane of the insulator-type transducer forms the floor of the container. Due to the damping material which is asymmetrically distributed relative to a normal axis to the membrane or, respectively, to the floor of the container, the transducer has a correspondingly asymmetrical transmission and reception characteristic and an asymmetrical transmission and reception lobe. A connecting line between the portions of damping material which are asymmetrically located in the inside of the insulator-type transducer can be visualized for the insulator-type transducer. Such connecting line extends perpendicularly to the surface which is normal to the membrane which is the floor of the container. The connecting line and the surface which is normal form a plane. The sound propagation or the sound reception characteristic in such plane is essentially a single radiation lobe which has the normal as a center line.
In a plane perpendicular to this plane, the radiation characteristic has a plurality of radiation lobes in which the middle radiation lobe has the surface normal to the membrane as a middle line, similar to the radiation lobe listed above.
Such an insulator-type transducer thus fundamentally has a broad radiation field for emission and/or reception in the one plane which is the vertical plane. In the plane perpendicular thereto, this transducer has a relatively narrow characteristic, so that an astigmatic sound characteristic results.